[PATCH] daemon: Break CHROOT_ENABLED into CHROOT_ENABLED and CLONE_ENABLED.

[Manolis Ragkousis]

Hello everyone,

This patch breaks CHROOT_ENABLED into CHROOT_ENABLED and CLONE_ENABLED.

If you check the code below, you will see that in case clone() is not
available it will use fork(), which is the case on Hurd.

But because CHROOT_ENABLED checks for others things, like mount.h and
pivot_root(), it never actually got to the second part of the code
below. This is fixed with my patch.

#if CHROOT_ENABLED
    if (useChroot) {
        char stack[32 * 1024];
        int flags = CLONE_NEWPID | CLONE_NEWNS | CLONE_NEWIPC | CLONE_NEWUTS |
SIGCHLD;
        if (!fixedOutput) flags |= CLONE_NEWNET;
        pid = clone(childEntry, stack + sizeof(stack) - 8, flags, this);
        if (pid == -1)
            throw SysError("cloning builder process");
    } else
#endif
    {
        pid = fork();
        if (pid == 0) runChild();
    }

Thank you,
Manolis

From 51d96cdea9aec679680c08add3a5ac03065760ba Mon Sep 17 00:00:00 2001
From: Manolis Ragkousis <manolis...@gmail.com>
Date: Sun, 7 Aug 2016 17:48:30 +0300
Subject: [PATCH] daemon: Break CHROOT_ENABLED into CHROOT_ENABLED and
 CLONE_ENABLED.

We need to check for CLONE_NEWNS only when we want to use the
Linux specific clone(). Otherwise we use fork().

* nix/libstore/build.cc (CHROOT_ENABLED): Break into CHROOT_ENABLED
and CLONE_ENABLED.
(DerivationGoal::startBuilder): Replace CHROOT_ENABLED with CLONE_ENABLED.
---
 nix/libstore/build.cc | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/nix/libstore/build.cc b/nix/libstore/build.cc
index ae78e65..b8a5ce6 100644
--- a/nix/libstore/build.cc
+++ b/nix/libstore/build.cc
@@ -51,7 +51,8 @@
 #include <linux/fs.h>
 #endif
 
-#define CHROOT_ENABLED HAVE_CHROOT && HAVE_SYS_MOUNT_H && defined(MS_BIND) && defined(MS_PRIVATE) && defined(CLONE_NEWNS) && defined(SYS_pivot_root)
+#define CHROOT_ENABLED HAVE_CHROOT && HAVE_SYS_MOUNT_H && defined(MS_BIND) && defined(MS_PRIVATE) && defined(SYS_pivot_root)
+#define CLONE_ENABLED defined(CLONE_NEWNS)
 
 #if CHROOT_ENABLED
 #include <sys/socket.h>
@@ -1998,7 +1999,7 @@ void DerivationGoal::startBuilder()
        - The UTS namespace ensures that builders see a hostname of
          localhost rather than the actual hostname.
     */
-#if CHROOT_ENABLED
+#if CLONE_ENABLED
     if (useChroot) {
 	char stack[32 * 1024];
 	int flags = CLONE_NEWPID | CLONE_NEWNS | CLONE_NEWIPC | CLONE_NEWUTS | SIGCHLD;
-- 
2.9.2